Floating work holder



Dec. 23, 1941. E. A. WALKER 2 2,266,928

FLOATING woRk HOLDER Filed Sept. 14, 1939 2 Sheets-Sheet 1 Dec. 23, 1941- E. A. WALKER v FLOATING WORK HOLDER 2 Shets-She'et 2 Filed Sept. 14, 1959 pamk m K-% s Patented Dec. 23, 1941 T OFFICE FLOATING WORK HOLDER Ernest A, Walker; Worceste Mass, s n rxto John Bath & Company, Worcester, Mass, acorporation of Massachusetts Application September 14, 1939, Serial No. 294,929

1 Claim.

This invention relates to machine tools and particularly to machines for tapping or reaming holes. In modern engineering practice, extreme accuracy is demanded, and reamed or tapped holes must be straight, accurately sized, and uniform in diameter throughout their length. It has been found difiicult to meet these requirements, particularly when using certain special steels which are unusually difiicult to work.

It is the general object of my invention to provide a floating work holder having limited free movement in a plane perpendicular to the axis of a tap or reamer. Other features of the invention relate to the provision of improved devices for controlling and limiting this free movement of the holder.

My invention further relates to arrangements and combinations of parts which will be hereinafter set forth and more particularly pointed out in the appended claim.

A preferred form of the invention is shown in the drawings, in which Fig. 1 is a partial side elevation of a tapping machine, with my improved work holder mounted therein;

Fig. 2 is a plan view of my improved work holder, looking in the direction of the arrow 2 in Fig. 1;

Fig. 3 is a detail sectional view, taken along the line 3-3 in Fig. 2;

Fig. 4 is a partial plan view of a ball retainer;

Fig. 5 is a partial end elevation, looking in the direction of the arrow 5 in Fig. 2;

Figs. 6 and 7 are partial side elevations of certain parts, looking in the direction of the arrows 6 and I in Fig. 2;

Fig. 8 is an end elevation of the work holder, looking in the direction of the arrow 8 in Fig. 2; and

Fig. 9 is a partial side elevation, looking in the direction of the arrow 9 in Fig. 2.

Referring to the drawings, I have shown my improved work holder mounted on a bracket or stand l9 supported by a machine frame II on which a tapping head I2 is vertically adjustable. A tap T is held in a chuck I4 mounted in the lower end of a vertical shaft l5 which forms part of the rotor of a reversible electric motor M. These parts may be of any usual construction.

The work W to be tapped is indicated as a block of metal resting on a face plate 29. If desired, the work W may be secured on the plate 29 by clamping bolts having their heads inserted in intersecting T slots 2| and 22 (Fig. 2). The work may also be in the form of a nut or other small item, held from rotation in a suitable fixture mounted on the face plate 29.

The plate 29 is supported on balls 25, which in turn rest on the upper surface of a base 26. Hardened steel wear plates 28 and 29 are embedded in the lower side of the plate 29 and in the upper side of the base 26 for engagement by the balls 25, and the balls are held centered over the wear plates 29 by a sheet metal retainer 39 having a series of holes 3| to receive the upper portions of the balls 25. The retainer 39 also has holes 32 near its corners, fitting loosely over studs 33 (Fig. 3) fixed in the base 26.

In the drawings I have shown the plate 29 supported on ten balls 25, but it will be understood that this number may be varied to suit operating conditions.

In order to limit the free movement of the plate 29, I provide a control link 49 (Figs. 2 and 8), one end of which is pivoted to a lug 4| on the end of the plate 29, and the other end of which is pivoted on a lug 42 on the end of the base 26.

A stud 59 (Figs.'2 and 9) is threaded in one side of the plate 29 and extends through a slotted lug 5| (Fig. 5) at the end of the base 26. Threaded collars 52 and lock nuts 53 on the stud 59 constitute adjustable stops to engage the lug 5| and thus limit endwise movement of the plate 29.

Adjusting screws 69 (Fig. 2) are threaded in lugs 6| extending upward from the base 26 and are held in adjusted position by lock nuts. 62.

The inner ends of the screws 69 form stops to limit transverse movement of the plate 29.

Lugs 65 (Fig. 8) project from the sides of the plate 29 adjacent the ends thereof and extend under offset lugs 66 extending upward from the base 26. The parts 65 and 66 have just sufiicient clearance so that the plate 29 can move freely on the balls but with very slight vertical lostmotion.- The lugs 66 may be formed, if desired, as separate pieces secured to the base 26 by screws 12 (Fig. 9).

A shield or skirt 19 (Fig. 8) may extend around the plate 29, to exclude dirt from the balls 25 and their supporting surfaces. Suitable holes 14 (Figs. 2 and 7) are provided for clamping the base 26 to the bracket l9.

Having described the details of construction of my improved work holder, it will be seen that the plate 29 is supported only by the balls 25, on which it may move very freely in a horizontal plane within limits determined by the link 49, stop collars 52 and stop screws 69, but upward movement of the plate 20 is prevented by the offset lugs 66.

It is found that work mounted on or carried by the plate 20 may be tapped or reamed with extreme accuracy, even if the axis of the tool is slightly eccentric to the axis of the spindle or shaft I5. The Work will follow the tool freely in ahorizontal plane, so that the tool cuts only its own size, even if rotating about an eccentric axis.

Greatly improved results have been attained in tapping nuts and other articles with the use of my improved floating work holder and the useful life of the tap is correspondingly prolonged.

Much more satisfactory results are attained than by use of floating tool holders which have been previously attempted but without very satisfac tory results.

Having thus described my invention *and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claim, but what I claim is:

In a machine tool, a work holder comprising a base, a face plate, anti-friction devices which provide a freely movable supporting bearing for said face plate on said base, a link having one end pivotally connected to an end projection of said base and having the other end pivotally connected to an associated end projection of said face plate, said link being substantially parallel to the plane of the face plate and also to the end surfaces of said base and face plate and being effective to limit the movement of said face plate projection to an are parallel to the plane of said face plate, said face plate also having a swinging movement about the pivot of said face plate projection,, and additional means to limit the 'movement of said face plate on said base in two substantially perpendicular directions in the plane of said'supporting bearing and relative to 

